Folegandros has too few and too small beaches. People not so much friendly, particularly during accomodation search. During the same travel, I visited also Milos and I found it much better. It would useful to have a tourist office, customer oriented, that could indicate and maybe directly provide information about rooms to let and hotels (with prices and availability). I had a lot of troubles to get in touch with someone and to book a room.
Folegandros is a pretty island but not so much enjoyable. The beaches are small, therefore they are always too full. I've been there on beginning of July and the people were too much compared to the island opportunity. Then accomodation are quite expensive and difficult to find. Don't sleep in the port area: boats arrived also during the night making you awake. I would suggest you stay there for 2-3 days and then continue your vacations somewhere else.